Question

过去两天我一直在努力解决返回数据问题。我真的需要帮助才能将数据显示在另一个.js文件中，但我似乎无法这样做。

从我所做的所有研究中，我知道我需要回调函数才能进行返回。当我输出 file1.js 中的数据时，它会显示，这是正确的。

但是，我需要访问 file2.js 中的返回数据，但它没有显示。我错过了什么吗？请帮助，非常感谢任何回应。谢谢。

请注意， file1.js 中的return语句接近代码的末尾。此外，当在函数外部访问时，我的“res”数组总是为空。为什么会这样？

file1.js

var sql = require("mssql");

// Create a configuration object for our Azure SQL connection parameters
var dbConfig = {
 server: "***", // Use your SQL server name
 database: "***", // Database to connect to
 user: "***", // Use your username
 password: "***", // Use your password
 port: 1433,
 // Since we're on Windows Azure, we need to set the following options
 options: {
       encrypt: true
   }
};

var obj = {};
var res = [];

// This function connects to a SQL server, executes a SELECT statement,
// and displays the results in the console.
function getProducts(callback) {
 // Create connection instance
 var conn = new sql.ConnectionPool(dbConfig);

 conn.connect()
 // Successfull connection
 .then(function () {

   // Create request instance, passing in connection instance
   var req = new sql.Request(conn);

   // Call mssql's query method passing in params
   req.query("SELECT sp.product_name, count(ss.product_id) as 'quantity' " +
      "FROM smartcoolerstocks ss JOIN smartcoolerproducts sp " +
      "ON sp.product_id = ss.product_id " +
      "GROUP by sp.product_name ")
   .then(function (recordset) {
     //console.log(recordset.recordset);
     
     conn.close();
     //NEED CALLBACK FUNCTION
     console.log(recordset.recordset.length);

      for(var i = 0; i<recordset.recordset.length; i++ ){     
                    res.push(recordset.recordset[i]);
        }
     
     
     callback(null,recordset.recordset);
     process.exit(1);
   })
   // Handle sql statement execution errors
   .catch(function (err) {
     console.log(err);
     conn.close();
   })

 })
 // Handle connection errors
 .catch(function (err) {
   console.log(err);
   conn.close();
 });
 
}



//call Fn for db query with callback
getProducts(function(err,data){
        if (err) {
            // error handling code goes here
            console.log("ERROR : ",err);            
        } else {            
            // code to execute on data retrieval
            //console.log("result from db is : ",data.recordset);   
            //return data.recordset;
            return res;                
            
        }
        
});
console.log(res); //WHY IS THIS EMPTY HERE?



module.exports = {
  getProducts(){},
  
};

块引用

file2.js

var myDB2 = require('./sqltest2');


console.log(myDB2.getProducts());

这是我在cmd中的输出：

在'7'之后，没有任何表现。

如果我设法从file1.js获取file2.js中的返回数据，那么我的IDEAL输出应该是以下内容：

Answer 1

您无法看到res，因为其竞争条件，console.log(res)早于recordset回调执行。
file1.js已经执行了getProducts函数，因此没有返回file2.js的数据。

var sql = require("mssql");
// Create a configuration object for our Azure SQL connection parameters
var dbConfig = {
  server: "***", // Use your SQL server name
  database: "***", // Database to connect to
  user: "***", // Use your username
  password: "***", // Use your password
  port: 1433,
  // Since we're on Windows Azure, we need to set the following options
  options: {
    encrypt: true
  }
};

var obj = {};
var res = [];

// This function connects to a SQL server, executes a SELECT statement,
// and displays the results in the console.
function getProducts(callback) {
  // Create connection instance
  var conn = new sql.ConnectionPool(dbConfig);
  conn.connect()
    // Successfull connection
    .then(function() {
      // Create request instance, passing in connection instance
      var req = new sql.Request(conn);

      // Call mssql's query method passing in params
      req.query("SELECT sp.product_name, count(ss.product_id) as 'quantity' " +
          "FROM smartcoolerstocks ss JOIN smartcoolerproducts sp " +
          "ON sp.product_id = ss.product_id " +
          "GROUP by sp.product_name ")
        .then(function(recordset) {
          conn.close();
          callback(null, recordset.recordset);
          process.exit(1);
        })
        // Handle sql statement execution errors
        .catch(function(err) {
          console.log(err);
          conn.close();
          callback(err, null);
        })
    }).catch(function(err) {
      console.log(err);
      conn.close();
      callback(err, null);
    });
}

module.exports = getProducts;

file2.js

var myDB2 = require('./sqltest2');
myDB2(function(err, data){
  if( err ) console.log(err);
  else console.log(data);
});

NodeJS返回SQL查询以传递到另一个文件

1 个答案: